Conventionally, an archive device is used to store digital contents such as music, movies, e-mails, medical images, and document data in an integrated fashion for a long period of time. The archive device is connected to a plurality of external devices via a network, stores various digital contents (hereinafter referred to as “data”) received from the external devices, and transmits the stored data to the external devices in accordance with a reference request from the external devices.
Specifically, the archive device includes a plurality of storage devices (disk array, tape library, and the like) and a processing device that performs write processing to the storage devices and read processing from the storage devices. The processing device writes data received from the external devices to the storage devices. At this time, the processing device generates and stores metadata (reception date, transmission source, storage position, and the like) for each received data. The processing device refers to the metadata in accordance with a request from a user, reads corresponding data from the storage devices, and transmits the data to the external devices.
To reduce recording volume, the archive device has a single instance function to prevent the same data as that having been already stored from being stored. Specifically, the archive device stores property information in which a hash value and a data size are associated with each other for each stored data. The archive device calculates the hash value of data newly requested to be stored, compares the calculated hash value and the data size of the data newly requested to be stored with the property information held in the archive device, and determines whether or not the same data has been already stored.
For example, when the archive device newly receives data whose hash value and data size are stored in the property information already held in the archive device, the archive device does not store the data, only generates metadata, links the generated metadata to data having been stored, and stores the metadata.
In recent years, a content delivery device that determines storage destination on the basis of a predetermined condition and stores data only in the determined storage destination to reduce recording volume is known (for example, refer to Japanese Laid-open Patent Publication No. 2004-30423). Specifically, for example, the content delivery device described above decides the storage destination in accordance with a remaining recording capacity and stores the data.